The present invention relates to the art of earth boring and, more particularly, to rolling insert cutter earth boring bits or cutterheads.
Rolling insert cutter earth boring bits and cutterheads provide an efficient way of boring holes through earth formations. Individual hard metal cutting insert elements are positioned in sockets in a rolling cutter body. The rolling cutter body is mounted to rotate on a bit body or cutterhead. The bit body or cutterhead is forced against the formations and rotated causing the cutter to roll over the face of the formations and the inserts to contact the formations to form the desired earth borehole.
Earth boring operations are conducted in various types of formations. These formations range from soft rock formations to hard rock formations. Prior to the present invention different types of cutters were used for boring in the different formations. For example, earth boring cutters having annular rows of projecting inserts separated by spaces were used for boring in soft rock formations. This allowed for the fast removal of the earth formations. In drilling in hard rock formations, earth boring cutters were utilized with the inserts positioned so that the entire face of the formation being drilled was contacted by the hard metal cutting inserts.